1. Field of the Invention
The present invention relates to a video signal reproduction apparatus for reproducing, as a progressive scan video signal, a video signal recorded in tape media, disk media, and the like, or a video signal carrying various image information such as movie materials or video materials through satellite broadcast, ground-based broadcast, and the like.
2. Description of the Related Art
Conventionally, video signals recorded in tape or disk media, or video signals transmitted through satellite broadcast, cable broadcast, or ground-based broadcast are commonly output as interlaced scan video signals by video signal reproduction apparatuses so that the video signals can be reproduced by image receivers. Recently, video signal reproducing apparatuses for converting interlaced scan video signals into progressive scan video signals are being introduced as monitors and projectors compatible with multi-scanning, or monitors for computers are becoming widespread.
The term “aspect ratio” as used herein refers to a ratio of the horizontal size of an image to the vertical size of the image as well as a ratio of the horizontal size of a monitor screen displaying an image to the vertical size of the monitor screen.
FIG. 12 is a block diagram showing a configuration of a conventional video signal reproducing apparatus 1200 which reproduces an information signal recorded in a disk-type medium. In FIG. 12, reference numeral 1 denotes a disk on which an information signal is recorded in an encoded and modulated signal form suitable for recording (or reproducing) in advance. The information signal includes a video signal and a determination flag indicating the type of the video signal.
The video signal reproducing apparatus 1200 includes: a pickup 2 for transforming an information signal recorded on the disk 1 to an electrical signal; a disk rotating apparatus 3 for rotating the disk 1 at a certain revolution-per-minute suitable for the disk 1; a material determination circuit 5 for determining the type of a video signal based on the determination flag included in the information signal; a converter 101 for converting the electrical signal transformed by the pickup 2 to an interlaced scan video signal and a progressive scan video signal; an encoder 7 for converting the interlaced scan video signal into an NTSC video format and outputs the result through an interlaced scan video output terminal 8 to an interlaced scan video monitor 103; and a color difference converter 10 for converting the progressive scan video signal output from the converter 101 into an analog color difference signal and outputs the result through a progressive scan video output terminal 11 to a progressive scan video monitor 104.
The converter 101 includes: an interlaced scan video signal reproduction circuit 4 for demodulating and decoding the electrical signal output from the pickup 2 and outputting the resultant signal as an interlaced scan video signal; an interlaced scan aspect ratio conversion circuit 6 for converting the aspect ratio of the interlaced scan video signal and outputs the result; an interlaced scan aspect ratio designating section 13 which is used by a user to designate the aspect ratio of the interlaced scan video monitor 103; an interlaced scan control circuit 12 for controlling the interlaced scan aspect ratio conversion circuit 6 based on the video signal type determined by the material determination circuit 5 and the type of the interlaced scan video monitor 103 designated by the interlaced scan designating section 13, and a progressive scan video signal conversion circuit 9 for converting the interlaced scan video signal having the converted aspect ratio into a progressive scan video signal and outputting the result.
The operation of the conventional video signal reproduction apparatus thus constructed will be described with reference to FIGS. 13 through 21.
FIG. 13 is a schematic diagram showing the structure of a video signal reproduced from the disk 1. In an interlaced scan video signal, one field of image is created in 1/60 second. One frame of image is composed of two fields. The number of vertical pixels of each of the two fields is 240. The scan lines of the two field are alternately arranged. In other words, a pixel of one field is disposed between two adjacent pixels of the other field in the vertical direction. In a progressive scan video signal, one frame is created in 1/60 second and the number of pixels of one frame in the vertical direction is 480. Both have a vertical frequency of 1/60 second. The number of horizontal scan lines of the progressive scan video signal is twice as many as that of the interlaced scan video signal. The horizontal scan frequency of the interlaced scan video signal is about 15.75 KHz, while that of the progressive scan video signal is double, i.e., about 31.5 KHz.
FIG. 14A is a schematic signal diagram showing the structure of the video signal reproduced from the disk 1. As shown in FIG. 14A, the video signal reproduced from the disk 1 has three forms. A first form of video signal represents an image having information which fills a full screen of 4:3 (hereinafter referred to as a 4:3 full image 301). A second form of video signal represents an image of 16:9 in the middle of the 4:3 screen, the upper and lower portions of the screen being shaded (hereinafter referred to as a 4:3 letterbox image 302). A third form of video signal represents an image having information which fills a full screen of 16:9 (hereinafter referred to as a 16:9 full image 303).
FIG. 14B shows the aspect ratio of the interlaced scan video monitor 103. As shown in FIG. 14B, there are two types of monitors for the interlaced scan video monitor 103, one monitor 304 having an aspect ratio of 4:3 and the other monitor 305 having an aspect ratio of 16:9.
FIG. 14C shows the aspect ratio of the progressive scan video monitor 104. As shown in FIG. 14C, there are two types of monitors for the progressive scan video monitor 104, one monitor 306 having an aspect ratio of 4:3 and the other monitor 307 having an aspect ratio of 16:9.
The interlaced scan video signal reproduction circuit 4 reads a video signal recorded on the disk 1 from an output of the pickup 2, reproduces an interlaced scan video signal, and outputs the result to the interlaced scan aspect ratio conversion circuit 6. The material determination circuit 5 reads the determination flag from an output of the pickup 2, determines the type of the video signal, and outputs the result as a determination signal to the interlaced scan control circuit 12.
A user designates the type (aspect ratio) of the interlaced scan video monitor 103 through which the user intends to output an interlaced scan video signal, using the interlaced scan aspect ratio designating section 13. The interlaced scan control circuit 12 controls the interlaced scan aspect ratio conversion circuit 6 based on a determination signal output from the material determination circuit 5 and the type (aspect ratio) of the interlaced scan video monitor 103 designated by the interlaced scan aspect ratio designating section 13.
FIG. 15 is a schematic diagram for explaining the operation of the interlaced scan aspect ratio conversion circuit 6. Assuming that the interlaced scan video monitor 103 has an aspect ratio of 4:3, the interlaced scan aspect ratio conversion circuit 6 has a function which compresses the 16:9 image 303 having an aspect ratio of 16:9 in the vertical direction. Specifically, in order to display the 16:9 image 303 on the 4:3 monitor 304 at the correct aspect ratio, 4 lines of information of an input video signal are subjected to a filtering process so that 3 lines of information are generated. Such a process is performed for the entire screen, so that the entire screen is compressed in the vertical direction. In this case, the displayed image has a correct aspect ratio (16:9), but leaving blanks in the upper and lower portions. Such portions are rendered black images. This aspect ratio conversion function can switch between a working state and a non-working state using the interlaced scan control circuit 12. In the case of the non-working state, the interlaced scan aspect ratio conversion circuit 6 outputs a received interlaced scan video signal without the aspect ratio conversion.
In FIG. 12, the user designates as the type (aspect ratio) of the 16:9 image 303, through which the user intends to output an image, the monitor 304 having an aspect ratio of 4:3 or the monitor 305 having an aspect ratio of 16:9 using the interlaced scan aspect ratio designating section 13. The material determination circuit 5 outputs the aspect ratio of an image source, i.e., one of the 4:3 full screen 301 or the 4:3 letterbox screen 302, and the 16:9 screen 303, to the interlaced scan control circuit 12. The interlaced scan control circuit 12 causes the aspect ratio conversion function of the interlaced scan aspect ratio conversion circuit 6 to be in the non-working state when the material determination circuit 5 indicates that the type of an image source is the 4:3 full image 301 or the 4:3 letterbox image 302. The interlaced scan control circuit 12 causes the aspect ratio conversion function of the interlaced scan aspect ratio conversion circuit 6 to be in the non-working state when the material determination circuit 5 indicates that the type of the image source is the 16:9 image 303 and the interlaced scan aspect ratio designating section 13 designates the monitor 305 having an aspect ratio of 16:9. Note that the interlaced scan control circuit 12 causes the aspect ratio conversion function of the interlaced scan aspect ratio conversion circuit 6 to be in the working state when the material determination circuit 5 indicates that the type of the image source is the 16:9 image 303 and the interlaced scan aspect ratio designating section 13 designates the monitor 304 having an aspect ratio of 4:3.
The encoder 7 converts an output of the interlaced scan aspect ratio conversion circuit 6 to the NTSC video format. The encoder 7 outputs an interlaced scanned image having the NTSC video format through the interlaced scanned image output terminal 8 to the interlaced scan video monitor 103.
FIGS. 16A through 16C are schematic diagrams for explaining the 4:3 full image displayed on an interlaced scan video monitor. As shown in FIG. 16A, the 4:3 full image 301 displayed on the 4:3 interlaced scan video monitor 304 has the correct aspect ratio. However, a 4:3 full image 301A displayed by the 16:9 interlaced scan video monitor 305 does not have the correct aspect ratio, so that the displayed image is extended horizontally as shown in FIG. 16B. The 16:9 interlaced scan video monitor 305 includes a 4:3 output switch function since the standard aspect ratio of an interlaced scan video signal is 4:3. As shown in FIG. 16C, the 16:9 interlaced scan video monitor 305 can display a 4:3 full image 301B having the correct 4:3 aspect ratio using the 4:3 output switch function.
FIGS. 17A through 17D are schematic diagrams for explaining the 4:3 letterbox image displayed on an interlaced scan video monitor. As shown in FIG. 17A, the 4:3 letterbox image 302 displayed on the 4:3 interlaced scan video monitor 304 has the correct aspect ratio. However, as shown in FIG. 17B, the 4:3 letterbox image 302A displayed on the 16:9 interlaced scan video monitor 305 does not have the correct aspect ratio, so that the displayed image is extended horizontally. The interlaced scan video monitor includes a 4:3 letterbox image output switch function since the standard aspect ratio of interlaced scan video signal is 4:3. With the 4:3 letterbox output switch function, as shown in FIG. 17C, the 4:3 letterbox image 302A is extended both upward and downward so that a 4:3 letterbox image 302B fills the full screen. Therefore, the interlaced scan video monitor 305 can display a 4:3 letterbox image at a correct aspect ratio of 16:9. An image source may have subtitle information 302C at the lower blank portion of an image. In this case, when a 4:3 letterbox image (302A) is extended upward and downward so that the 4:3 letterbox image (302B) fills a full screen and is displayed at a correct aspect ratio of 16:9, the subtitle information 302C disappears. To avoid such a situation, the interlaced scan video monitor 305 has a switch function with which the subtitle information 302 is shifted upward to be viewed on the screen.
FIGS. 18A through 18C are schematic diagrams for explaining a 16:9 image displayed on an interlaced scan video monitor. As shown in FIG. 18A, when a 16:9 image 303A is displayed as it is on the 4:3 interlaced scan video monitor 304, the image does not have the correct aspect ratio, such that the displayed image is extended vertically. However, if the user teaches the interlaced scan aspect ratio designating section 13 that an interlaced scan monitor to be connected to the apparatus 1200 is the 16:9 interlaced scan monitor 305, the interlaced scan aspect ratio conversion circuit 6 is activated and the aspect ratio is converted so that an image (16:9 image 303B) is correctly displayed as shown in FIG. 18B. In addition, as shown in FIG. 18C, the 16:9 interlaced scan video monitor 305 displays a 16:9 image 303 at a correct aspect ratio of 16:9.
Specifically, in the conventional video signal reproduction apparatus 1200, the interlaced scan video monitor can display images having a correct aspect ratio in any combination of 3 types of image sources, i.e., the 4:3 full image, the 4:3 letterbox image, and the 16:9 image with 2 types of video monitors, i.e., the 4:3 monitor and the 16:9 monitor.
An output of the interlaced scan aspect ratio conversion circuit 6 is input to the progressive scan video signal conversion circuit 9. The progressive scan video signal conversion circuit 9 converts an input interlaced scan video signal to a progressive scan video signal, and outputs the result. The color difference converter 10 converts the progressive scan video signal to a color difference video signal, and outputs the progressive scan video output through the progressive scan video output terminal 11 to the progressive scan video monitor 104.
FIGS. 19A and 19B are schematic diagrams for explaining a 4:3 full image displayed on a progressive scan video monitor. As shown in FIG. 19A, the 4:3 full image 301 displayed on the 4:3 progressive scan video monitor 306 has the correct aspect ratio. However, as shown in FIG. 19B, a 4:3 full image 301C displayed on the 16:9 progressive scan video monitor 307 does not have the correct aspect ratio, so that the displayed image is extended horizontally. Here, the 16:9 progressive scan video monitor is a monitor intended to receive a high-definition television signal, and has a standard aspect ratio of 16:9 but does not include a 4:3 output mode. Therefore, a 4:3 full image is not displayed at the correct aspect.
FIGS. 20A and 20B are schematic diagrams for explaining a 4:3 letterbox image displayed on the progressive scan video monitor. As shown in FIG. 20A, the 4:3 letterbox image 302 displayed on the 4:3 progressive scan video monitor 306 has the correct aspect ratio. However, as shown in FIG. 20B, a 4:3 letterbox image 302C displayed on the 16:9 progressive scan video monitor 307 does not have the correct aspect ratio, so that the displayed image is extended horizontally. As described above, the 16:9 progressive scan video monitor 307 is a monitor intended to receive a high-definition television signal, and has a standard aspect ratio of 16:9 but does not include a 4:3 output mode. Therefore, a 4:3 full image is not displayed at the correct aspect.
FIGS. 21A through 21C are schematic diagrams for explaining a 16:9 image displayed on an interlaced scan video monitor. As shown in FIG. 21A, when a 16:9 image 303C is displayed as it is on the 4:3 progressive scan video monitor 306, the image does not have the correct aspect ratio, such that the displayed image is extended vertically. However, if the user teaches the interlaced scan aspect ratio designating section 13 that a progressive scan video monitor to be connected to the apparatus 1200 is the 16:9 interlaced scan monitor 307, the interlaced scan aspect ratio conversion circuit 6 is activated and the aspect ratio is converted so that an image (16:9 image 303D) is correctly displayed as shown in FIG. 21B. In addition, as shown in FIG. 21C, the 16:9 progressive scan video monitor 307 displays a 16:9 image 303 at a correct aspect ratio of 16:9.
As described above, in the conventional video signal reproduction apparatus 1200, there is a problem in that a 4:3 full image and a 4:3 letterbox image cannot be displayed on a 16:9 video monitor at the correct aspect ratio.
Further, when a 4:3 letterbox image includes a subtitle at a lower portion of the screen, there is a problem in that if the 4:3 letterbox image is extended upward and downward so as to be displayed at the correct ratio on a 16:9 video monitor, the subtitle disappears.
Accordingly, there is a demand for a video signal reproduction apparatus in which in any combination of 3 types of image sources, i.e., the 4:3 full image, the 4:3 letterbox image, and the 16:9 image with 2 types video monitor, i.e., the 4:3 monitor and the 16:9 monitor, any image can be displayed at the correct aspect ratio. Even when the 4:3 letterbox image includes a subtitle at a lower portion of the screen, the disappearance of the subtitle needs to be prevented.